The present invention relates generally to apparatus and related methods for repairing or replacing deteriorated joints, and is especially adapted for use in repairing or replacing the human knee joint.
The joint of the human knee is formed by the low friction and movable contact between the femur (thigh bone) and the tibia (shin bone). The upper extremity of the tibia has a surface defined by a generally centrally located prominence, referred to as the intercondular eminence, extending generally longitudinal in the direction of joint motion, the eminence fitting within a corresponding groove in the distal femur. The tibial bearing surface includes a pair of tibial plateaus on opposite sides of the longitudinal eminence which are adapted to act as bearing surfaces for the two ball-shaped bearing surfaces on opposite sides of the femoral groove, called the "femoral condyles". The articulations of the femur and tibia are held together in a movable relationship by the knee cap (patella), and ligaments and muscles extending both inside and outside of the knee, with soft fluidic, cushioning tissue extending between the bearing surfaces.
Frequently, a deteriorated knee requires the replacement of the bearing surfaces of the upper portion of the tibia and the lower portion of the femur; this is customarily referred to as a "total knee replacement". Because a total knee replacement involves the cutting away of a substantial portion of the upper portion of the tibia and the lower portion of the femur and with replacement of those two portions with artificial components, then these artificial components must employ low friction surfaces which are capable of cooperating together to simulate as closely as possible the natural movement of the human knee before surgery.
A total knee replacement usually involves the removal of approximately between 0.5 to 1.5 centimeters of the upper portion of the tibia, including both the longitudinal eminence and the tibial plateaus, leaving a relatively flat surface into which a rigid metal support member is inserted. Then, a low friction bearing member is affixed to the support member, with the low friction member including a longitudinal prominence simulating the eminence and with bearing surfaces simulating the tibial plateaus. A lower end portion of the femur is then removed, and a member having bearing surfaces replicating the femoral condyles is then affixed to the remaining end of the femur.